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Canepa's Car Wash (Pacific Avenue) Problem Assessnrent Report and Corrective Action Plan Pagc I 1 8- hour time- weighted average recommended limit of 0325 mghn' . However, according to the sofrivare, this also would produce an individual cancer risk of 2 . 0 in 10,000, greater than the target level of one in one million . Outdoor air exposures were two orders of magnitude lower. The complete software printout IS included as Appendix B. 7. 0 CORRECTIVE ACTION PLAN 7. 1 DESCRIPTION OF CORRECTIVE AC'T'ION STRATEGIES Evaluation of the remedial alternatives for soil and groundwater at the site is complicated because of saturation of the contaminated soil by the 20-foot rise in the elevation of the water table, Although it is apparent from the available data that a large but unknown mass of volatile organic compound was removed by the soil vapor extraction system, significant VOCs remain in the saturated soil . The remedial alternatives are limited by the site use constraints. Due to the depth of the soil contamination (below the groundwater, more that 30 feet deep) excavation and ex situ treatment of the soil is not possible. Also, because of the urban location and congested use of the site, very little space is available for ex situ treatment units. Additionally, the soil vapor extraction system currently in place has removed a significant portion of the soil vapor contamination above the groundwater, but it is not capable of efficient VOCs removal from the soil below the groundwater. Continued operation of the system as a sole remediation alternative is not a feasible remedial alternative. Based on the contaminants of concern and the limitations noted, the following alternatives have been considered: 1. In sitar attenuation through passive biodegradation; 2. Enhanced in situ bioremediation and/or chemical oxidation; 3. Soil Vapor Extraction; 4. Air Sparging; 6. Ex situ groundwater treatment (pump and treat); and 6. Combinations of Alternatives 2 through 5 . Alternative I , in situ attenuation through passive biodegradation, would rely on natural biodegradation of the volatile organic compounds in the soil and water. Conceptually, thenativebacteria would rely on the petroleum hydrocarbons for their carbon source and the nutrients and oxygen dissolved in the groundwater to enhance the bacterial activity. There is evidence for active biodegradation in the area of soil borings SB- 1 and SB-2 prior to saturation of the soil by the rising water table. Biological activity with limited availability of oxygen in the soil is suggested by the olive-gray and blue-gray soil colors, indicating that the oxygen necessary to sustain the biological activity was derived from reduction of oxide minerals . The time required to achieve acceptable water quality cannot be estimated and there would be no down-gradient containment of the plume; however, costs would be limited to those for groundwater monitoring and monitoring for natural attenuation. Alternative 2, enhanced in situ bioremediation and/or chemical oxidation, would augment the natural biodegradation discussed above. Augmentation can involve nutrients, specially developed microbes, and/or electron acceptors (oxygen being the most common electron acceptor). It is likely, based on the length of time the contamination has been present in the subsurface, that microbes adapted to the environment and contamination have sufficiently developed. However, nutrient or oxygen addition could accelerate the microbial _ activity. Nutrient addition would require an analysis of nutrient deficiencies (if 1 � A LJ CONDOR